Processes for recycling used or in-process defective batteries (hereinafter referred to as “waste batteries”), such as waste lithium-ion batteries, and recovering their valuable metals are broadly divided into dry and wet processes.
A dry process includes melting crushed waste batteries, separating valuable metals, which are to be recovered, from other less valuable metals and materials by harnessing the difference in oxygen affinity between them, and recovering the valuable metals. Specifically, such a dry process includes oxidizing less valuable elements, such as iron, as much as possible to form slag and suppressing the oxidation of valuable materials, such as cobalt, as much as possible to recover the valuable materials in the form of an alloy.
For example, Patent Document 1 discloses that valuable metals such as a nickel and cobalt are recovered in the form of an alloy by using a high-temperature heating furnace and adding a SiO2/CaO-based flux to waste batteries, and at this time, the slag has a composition containing 20% or more of iron in terms of metallic iron, and 20% or less each of nickel and cobalt, with the SiO2/CaO ratio being 1 or greater. The melting temperature in the Examples is 1450 C.
[Patent Document 1] U.S. Pat. No. 7,169,206